Qiua, Jingxin 1; Nelsona, Sharon H. 1; Spethb, Robert C. 2; Wanga, Donna H. 1,3
Abstract:
Objective: Previous studies indicate that the adrenal gland plays a compensatory role in the maintenance of blood pressure in chemically sympathectomized rats. However, the mechanisms responsible for compensatory adrenal responses are poorly understood. This study examined the regulation of adrenal growth and type 1A, 1B, and type 2 angiotensin II (Ang II) receptor (AT1A, AT1B and AT2) expression in the adrenal gland induced by sympathectomy.
Methods: Five-week-old male Sprague-Dawley rats were treated with either guanethidine (50 mg/kg per day, intraperitoneally) or vehicle for 5 weeks. Norepinephrine and epinephrine levels in the atrium of the heart were measured by high-pressure liquid chromatography. Plasma renin activity was determined by radioimmunoassay. Adrenal AT1 and AT2 receptor density was determined by radioligand binding assay. Adrenal AT1A, AT1B and AT2 mRNA levels were determined by Northern blot analysis.
Results: Norepinephrine and epinephrine levels in the atrium of the heart were decreased 86% (P <>0.05), were increased in guanethidine-treated rats compared with vehicle (P < r =" 0.9," r =" 0.6," r =" 20.01,"> 0.05) expression.
Conclusions: Impairment of the sympathetic nervous system with guanethidine withdraws the normal stimulation of this system on the circulating renin-angiotensin system, but upregulates the expression of adrenal Ang II receptors. Increased expression of adrenal AT2 and AT1A receptors may play an important role in adaptive adrenal hypertrophy and hormonal responses to sympathectomy.